An internal combustion engine of related art in which a connecting rod with an integral big end part is connected to an assembly-type crankshaft appears for example in JP-A-6-280847.
A connecting rod for an internal combustion engine of related art that is connected to a piston by a spherical joint appears for example in JP-A-9-144879. The content of JP-A-9-144879 will be explained with reference to FIG. 12.
A crankshaft shown in JP-A-6-280847 is an assembled member made up of a first section, a second section, a third section and a fourth section; a recess is provided in each of a first crank web mounted on the first section and a second crank web mounted on the second section, and a pin is rotatably fitted in bearings in these recesses.
The connecting rod has an integral big end, a hole is provided in the big end, and a pin is rotatably fitted in this hole.
When the crankshaft is made an assembly type like this, unnecessary metal can be removed to reduce its weight, and by the connecting rod being made of integral big end type, compared to a connecting rod with a two-piece big end, bolts can be dispensed with and weight can be reduced.
When the above-mentioned bearings between the recesses and the pin are needle bearings, the big end of the connecting rod becomes large, the weight of the connecting rod becomes large, and consequently the above-mentioned weight-reducing effects of the assembly type crankshaft and the integral big end type connecting rod are reduced.
Thus, to reduce the weight of an internal combustion engine, for example to raise the speed, the output and the durability of the internal combustion engine, it is important to reduce the weights of the main moving parts, and if weight-reduction of the main moving parts is not carried out comprehensively, a large, synergetic effect cannot be obtained. By the combination of main moving parts, not only reduced weight but also other effects such as strength and ease-of-assembly benefits can be expected.
The connecting rod 200 shown in FIG. 12 is a member having a convex spherical surface 202 formed on a small end part 201, and this convex spherical surface 202 fits slidably against a concave spherical surface 204 provided on the piston 203 side. That is, the connecting rod 200 and the piston 203 are connected by a spherical joint 205 formed by the convex spherical surface 202 and the concave spherical surface 204.
The crankshaft 200 described above swings along with the reciprocal motion of the piston 203 and rotates a crankshaft (not shown).
Accordingly, if the weight of the main moving parts such as the crankshaft 200, the piston 203 and the crankshaft (the parts that transmit power in the internal combustion engine) can be reduced, their respective inertias decrease, the loads on the areas supporting these parts can be reduced, and higher output can be obtained through higher internal combustion engine speeds.
Thus, in the internal combustion engine, means have been awaited for achieving higher speeds, higher power and better durability through weight-reduction of the connecting rod itself and comprehensive weight-reduction of the other main moving parts and for increasing for example strength and ease-of-assembly through the effective combination of main moving parts.